1. Field of the Invention
The present invention relates to a fastening device for attaching a heat sink to a heat producer and, more particularly, to a fastening device for easily attaching a heat sink to a heat producer supported on a board without risk of jamming of an elastic member during assembling operation.
2. Description of Related Art
FIG. 1 shows a device for attaching a heat sink to a CPU (central processing unit), which is supported on a board 90 provided with through-holes 91. The heat sink includes a cover 92 having a plurality of tubes 93 for receiving respective fastening members 94.
Each of the fastening members 94 has a tapered, enlarged resilient head 95 with a diameter larger than that of the through-hole 91, and has a plurality of openings 96 to make the tapered, enlarged head 95 deformable and resilient enough to squeeze through the through-hole 91. The enlarged head 95 is then engaged with an underside of the board 90 by an elastic force of a compressed elastic member 97 fitted around the fastening member 94, thus attaching the heat sink to the CPU.
In the prior art, however, the elastic member 97 has a uniform diameter at its full length. Being compressed during the assembling operation, the elastic member 97 readily becomes larger in diameter and raises its upper end to a larger diameter section of the fastening member 94, thus being jammed between the fastening member 94 and the tube 93. The jammed elastic member 97 results in inconvenient detaching operation for the heat sink from the CPU, if it is necessary.
The object of the present invention is to provide a fastening device for easily attaching a heat sink to a heat producer supported on a board without risk of jamming of an elastic member during assembling operation.
To achieve the aforementioned objects, the present invention provides improved devices for attaching a heat sink to a heat producer which is supported on a board having through-holes aligned with mounting holes of the heat sink. Each of the improved devices includes a tube adjacent to one mounting hole, a fastening member movably received in the tube, and an elastic member fitted around the fastening member. The fastening member has an enlarged resilient head, a shoulder and a neck extending between the head and the shoulder, with the head adapted to squeeze through the mounting hole and the through-hole for engaging with a side of the board opposite to the tube. The elastic member includes a minimum diameter section fitted around the heck and abutting the shoulder of the fastening member, a maximum diameter section abutting a distal end of the tube, and an intermediate diameter section stretchable between the minimum and maximum diameter sections.
Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.